This creates a line at each sidebar widget but breaks before the next widget and starts again. Also, when I change the px, it doesn’t work. I was hoping for a 1px solid line, color #728cb0, that doesn’t break at all and separates content from right sidebar.

I found this CSS :

.sidebar-right-wrap {
border-left: 1px solid #728cb0;
}

It is almost perfect. It doesn’t follow the sidebar all the way to the footer like I would like, but it’s good enough for now.